Multi-purpose piston ring assembly



Aug. 23, w KNOEBEL MULTI-PURPOSE PISTON RING ASSEMBLY Filed May 10, 19632 Sheets-Sheet 1 F l G. l F l G. 2.

6 2 e m FIG 3 INVENTOR.

WA TER C.KNO BEL BY A.

ATTORNEYS Aug. 23, 1966 w. c. KNOEBEL MULTIPURPOSE PISTON RING ASSEMBLY2 Sheets-Sheet 2 Filed May 10, 1963 FIGS.

FIG.6.

INVENTOR. WALTER C KN EBEL ATTORNEYS United States Patent 3,268,234MULTi-PURPSSE PISTGN RING ASSEMBLY Walter C. Knoebel, St. Louis County,Mo assignor to McQuay-Norris Manufacturing (Iompany, St. Louis, Mo., acorporation of Delaware Filed May 10, 1963, Ser. No. 279,413 3 Claims.(#Cl. 277-139) This invention relates to piston rings and morespecifically to a piston ring which is so constructed that, wheninstalled in one kind of a piston, it will serve certain purposesprimarily, and, when installed in another kind of piston, it will servecertain other purposes primarily. One of the advantages of such a pistonring construction is its adaptability.

This description refers to piston rings for one, or more, purposes. Itshould be understood that these purposes include piston rings intendedprimarily for control of compression and combustion gas pressures(compression rings) and rings primarily intended for control oflubrication (oil control rings). In this case, a combined purpose ringis one adapted to serve either as a compression ring, or an oil controlring. This invention relates to piston rings for combined purposesaccording to this definition. In other words, this invention relates toa piston ring of the kind in which the purpose primarily served isdetermined by the installation. The purpose, or purposes, served by thepiston ring, according to this invention, therefore, depend upon thetype of piston in which it is installed, its location on that piston,and the characteristics of the piston ring groove in which the pistonring is installed.

The type of piston, preferred by engine manufacturers, changes from timeto time. At one time, a piston was used extensively which had a head andskirt, and the ring belt on the head contained four ring groovesseparated by lands. Various combination of rings were used, but usuallyat least the two top rings were compression rings. At the present time,the preferred piston has a head and a skirt in which the head contains aring belt with three piston ring grooves separated by lands. Competitionbetween engine makers, however, may produce a trend to pistons of thetype having only two piston ring grooves in the ring belt about the headof the piston. Engineers have long recognized the competitive advantagesto be realized by decreasing the number of ring grooves and,accordingly, the number of piston rings. The decrease in the number ofpiston ring grooves and rings shortens the ring belt and the length ofthe piston. A shorter piston means a shorter cylinder and an overalldecrease in the size of the engine and its weight. This conclusion isconfirmed by statements found in some prior patents, notably Bowers2,414,013.

As of the present time, the engine makers prefer the type of piston,above described, with a ring belt containing three separate ringgrooves, two for compression rings at the top and one for an oil ring atthe bottom. The piston ring, according to this invention, is adapted foruse in a bottom ring groove as an oil control ring in this or any othertype of multi-groove piston.

Looking into the future, it may occur that the type of piston using buttwo ring grooves in the ring belt becomes preferred. This type of pistonuses one compression ring, or fire ring, in the top groove of the pistonand one dual purpose ring for both compression and oil control in thelower groove. As far as weight saving in the engine is concerned, thesame advantages are to be gained from going from a three ring type ofpiston to a two ring type of piston as were gained by the change from afour ring type of piston to a three ring type of piston. Should such achange be in the offing, it would be made equally attractive to thepiston ring manufacturer who has in production a piston ring to serveeither a single purpose of oil control, or the dual purpose of oil andcompression, required by a combined purpose ring in the piston havingbut two piston ring grooves in the ring belt. This invention providessuch a piston ring.

Thus, it is one of the objects of this invention to provide a pistonring assembly which is adapted to more than a single kind ofinstallation and adapted to serve more than a single specializedpurpose.

It is a further object of this invention to provide a piston ringadapted to both a single specialized purpose, or adapted to servecombined purposes depending solely upon the kind of installationprovided.

It is a further object of this invention to provide a piston ringassembly having a spring type spacer-expander coacting with a splitpiston ring in such a way as to apply a force with respect to the pistonring which does not interfere with any initial set of the ring in thegroove.

It is still another object of this invention to provide a piston ringassembly for a multi-purpose ring which includes a spring typespacer-expander and a pair of expansible piston ring elements soconstructed that the expansive force of the spring produces a twist inopposite directions in the piston ring elements.

According to this invention, the multi-purpose piston ring is anassembly of two or more elements, as an example, a pair of splitexpansible piston ring elements, or rails, and a spring typespacer-expander ring element located between the piston rings, or rails.On the inner radial face of each piston ring element is acircumferentially extending shoulder. Each piston ring element is alsochamfered at its inner periphery at its outer edge, or otherwise formedto impart a permanent set, or twist, to the piston ring element whichwill tend to cause the inner radial faces of the pair of spaced pistonring elements to diverge radially outwardly and converge radiallyinwardly.

The spacer-expander spring ring element is similar to that shown in thepatent application of Theodore P. Rodenkirchen, Serial No. 163,462,filed January 2, 1962, now Patent No. 3,140,096, but it differs in itsposition with respect to the piston rings or rails. Preferably, it islocated wholly within the inside periphery as well as the outsideperiphery of each of the piston ring elements and there existsconsiderable clearance between the inner periphery of thespacer-expander ring element and the inner periphery of each rail.

The spring type spacer-expander type ring element is a ribbon of springsteel formed as a split ring of the reverse loop type. The ends arearranged to abut to make it a circumferentially compressible spring.Such a circumferentially compressible spring will change diameter inresponse to balanced radial forces which squeeze the ring elements intothe groove of the piston, but the entire piston ring assembly will floatin the piston groove to a position in which such compressive forces arein balance. The assembly of ring elements are accordingly full floatingand non-bottoming in the piston ring groove.

Preferably, the outwardly extending loops, or humps, of the spring typespacer-expander ring element are constructed to be more resilient thanthe inwardly extending loops, all as described in the aforesaid patentapplication of Rodenkirchen. The upper and lower edges of the ribbonforming the spacer-expander are notched circumferentially, and thesenotches engage the inner periphery of the circumferentially extendingshoulders on the top and bottom piston ring elements to urge theseelements radially outwardly of the piston grooves and against thecylinder walls.

As heretofore mentioned, each piston ring element is preferably made tohave a permanent set, or twist.

larged scale. Only a portion of the head of the piston is shown whichcontains the ring belt. In FIG. 5, the piston head 40 has a ring belt,generally indicated as 41, containing three or more piston ringgroove-s, three of which are shown, 42, 43 and 44. The top grooves 42and 43 contain rings 45 and 46. Top ring 45, or the one above it, as thecase may be, is a so-called fire ring. The primary function of theserings 45 and 46 is to seal off the leakage of compression, or combustiongases, from escape between the piston 40 and its cylinder wall. Inpiston 49, the lower piston ring groove 44 is especially formed toaccommodate a piston ring which is primarily intended for the purpose ofoil control. Accordingly, this .ring IgIOOVe 44 is provided with oildrainage slots 49 and 51 so arranged to return the oil accumulated bythe piston ring in that groove back to the crank case of the engine. Toillustrate, one of the uses of the instant invention, a ring assembly,constructed as aforedescribed, has been shown installed in the groove44. Piston ring elements, here shown as rails 1, are held spaced by aspacercxpander spring, such as 14 heretofore described. Since theserails 1 are normally of dish-shape, as shown in FIG. 3, there is asealing point 53 between the top rail 1 located at the edge of thepistol ring groove 44. Likewise, there is a sealing point 54 between thesurface of the lower rail 1 and the lower edge of the piston ring groove44. This is due to the inherent shape imparted to the rails by theirmethod of manufacture. In addition, there is a pressure point 55 betweenthe shoulder 22 and the face 11 of the shoulder of the top rail 1, and asimilar pressure point 56 between the shoulder 24 and the face 11 of theshoulder 10 of the bottom rail 1.

' Neither of these pressure points 55 or 56 will interfere in any waywith the permanent set in the piston ring element, shown here asrails 1. Thus, the action of this piston ring is such that on the upperstroke, oil is prevented from escaping past the seal point 53, and, ondown stroke, oil is prevented from escaping past the seal point 54. Ithas been discovered that better oil control can be obtained if thesesealing points, or zones, 53 and 54 remain effective, and especially soif all of the expansive forces on the piston ring elements 1 are such asnot to interfere with, and, if desired, augment the set imparted tothese elements.

Turning now to FIG. 6, this view illustrates on an enlarged scale thering belt portion in another type of piston 75. This type of piston hastwo or more ring grooves. Only two are shown. The top groove 76, or, ifmore than two grooves are provided, then this and the ones above,receive a ring, or rings, 77, the primary purpose of which is to sealthe clearance between the piston 75 and the cylinder wall against theleakage of gases due to compression, or combustion, pressures. The ringbelt on this piston 75 also contains a lower ring groove, generallyindicated by the reference character 88. This ring groove 88 has an oildrainage slot, or slots, 81 connecting with the piston ring groove 88.There is also an oil drainage slot 82. In the bottom of the ring groove88 are a pair of annular slots 85 and 86, each of which receives theinner periphery of one of a pair of piston ring elements here shown asrails 1 of the piston ring assembly. Since these elements have a dishedconfiguration and are located in the slots 85 and 86, there will be twosealing points on each ring. On the upper element 1, there will be asealing point along a circumferential line 63 at the edge of slot 88 andanother along a circumferential line 79 at the inner edge of the rail 1.Thus, any combustion gases passing the ring 77 and behind the upper rail1 will be trapped in the groove 86 behind the rail 1 forcing the railoutwardly to seal against the escape of gas pressure between its outerperiphery and the cylinder wall.

The lower piston ring element, also shown here as a rail, is alsodished, consequently, the same action will prevail, that is, there willbe a sealing point at the edge of the groove 88, indicated as 64,extending circumferentially of the piston. These two seals will preventthe escape of oil upwardly past the lower rail 1 into the piston ringgroove 88. The upper element 1 of the assembly will act primarily as acompression ring because its outward pressure against the cylinder wallwill vary directly with the gas pressure acting on its inner peripheryto force it outwardly. The lower element 1 will act primarily as an oilcontrol ring preventing the escape of oil into the piston ring groove88. Expander 14 acts as the spacer exerting an outward pressure on theface 11 of the shoulder 10 of the upper element 1 at the points 55. Thelower element 1 is urged outwardly by the shoulders 24 acting on theface 11 of the shoulder 10 at a series of points 56. Neither the points55 or 56 are disposed to interfere in any way with the permanent set inthe piston ring elements.

The piston 90, shown in FIG. 7, is of a type similar to that shown inFIG. 6. It has only a pair of piston ring grooves, as shown, in the ringbelt, but there may be several. The upper groove 93 receives the pistonring assembly, such as heretofore described. In the bottom of the ringgroove 94 is an annular groove 92 receiving the upper piston ringelement 1. Contact between the upper element 1 and the groove 94 is suchas to produce a sealing point 98 circumferentially of the pistonadjacent the outer edge of the groove and another 96 at the innerperipheral edge of the element 1. Lower element 1 also is dished so asto provide a seal at the point 99 extending around the periphery of thepiston 90.

The three diiferent installations in FIGS. 5, 6 and 7 determine theprimary purpose of the piston ring assembly, according to thisinvention. In FIG. 5, the purpose of the assembly is primarily as an oilcontrol ring. In FIGS. 6 and 7, the assembly is dual purpose in that thetop element acts as a compression ring, while the bottom acts primarilyas an oil control ring. The pur pose of the two installations in FIGS. 6and 7 is similar, but the double sealing action on each element 1 ischaracteristic of only the installation shown in FIG. 6. Both elements 1in FIG. 6 have a double seal at the outer and inner periphery of each.For this reason, FIG. 6 is the preferred manner of installation for adual purpose ring constructed in accordance with this invention.

Changes in and modifications of the construction described may be madewithout departing from the spirit of my invention or sacrificing itsadvantages.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. In a piston ring assembly for a cylinder and piston combination, saidpiston having a peripherally extending groove with upper and lowerlands, said ring assembly including a pair of substantially identicalcylinderengaging rings, and a circumferentially expansible andcontractible non-bottoming expander spring disposed axially between saidrings and in radially-outward biasing relation therewith, theimprovement which comprises: each cylinder-engaging ring having:

(1) an outer peripheral face for engaging the cylinder, and an innerperipheral face radially remote from said outer peripheral face,

(2) a side face for engaging one of said lands; said side face extendingbetween said inner and said outer peripheral faces, and, at anycross-section taken along a radius, being substantially flat but out ofnormal to the axis of said ring in the sense that said side faces of therespective cylinder-engaging rings converge toward said axis;

(3) an opposite side face having a circumferentially extending, axiallyprojecting rib intermediate said peripheral faces, said rib providing anexpanderthrust-receiving-surface which makes an angle of not more thanwith said opposite side face and which surface is located closer to saidinner peripheral face than to said outer peripheral face;

said groove having a sub-groove embracing the inner periphery of theuppermost one of said cylinder-engaging rings and engaging the oppositeside (3) thereof adjacent its inner periphery; said rings being disposedwith their respective ribs addressed toward each other and theexpander-tihrust-receiving-surface of each rib being so engaged withsaid expander spring that the radially outward biasing action of theexpander is delivered to said ribs substantially free of componentswhich tend to decrease the converging relationship between thefirstmentioned side faces of the respective cylinder-engaging rings.

2. The piston ring assembly of claim 1 wherein the expander spring is astrip of spring material corrugated to define a series of inner humpsand a series of outer humps in alternating relationship, and therespective series of humps are astride the ribs of said rings.

3. The piston :ring assembly of claim 1 wherein the UNITED STATESPATENTS 2,231,801 2/1941 Cords 277-439 2,877,072 3/1959 Pien 2771393,000,678 9/1961 Braendel 277-139 3,004,811 10/ 1961 Mayfield 277---1393,024,029 3/1962 Brenneke 277l39 LAVERNE D. GEIGER, Primary Examiner.

SAMUEL ROTHBERG, Examiner.

L. RANEY, J. MEDNICK, Assistant Examiners.

1. IN A PISTON RING ASSEMBLY FOR A CYLINDER AND PISTON COMBINATION, SAIDPISTON HAVING A PERIPHERALLY EXTENDING GROOVE WITH UPPER AND LOWERLANDS, SAID RING ASSEMBLY INCLUDING A PAIR OF SUBSTANTIALLY IDENTICALCYLINDERENGAGING RINGS, AND A CIRCUMFERENTIALLY EXPANSIBLE ANDCONTRACTIBLE NON-BOTTOMING EXPANDER SPRING DISPOSED AXIALLY BETWEEN SAIDRINGS AND IN RADIALLY-OUTWARD BIASING RELATION THEREWITH, THEIMPROVEMENT WHICH COMPRISES: EACH CYLINDER-ENGAGING RING HAVING: (1) ANOUTER PERIPHERAL FACE FOR ENGAGING THE CYLINDER, AND AN INNER PERIPHERALFACE RADIALLY REMOTE FROM SAID OUTER PERIPHERAL FACE, (2) A SIDE FACEFOR ENGAGING ONE OF SAID LANDS; SAID SIDE FACE EXTENDING BETWEEN SAIDINNER AND SAID OUTER PERIPHERAL FACES, AND, AT ANY CROSS-SECTION TAKENALONG A RADIUS, BEING SUBSTANTIALLY FLAT BUT OUT OF NORMAL TO THE AXISOF SAID RING IN THE SENSE THAT SAID SIDE FACES OF THE RESPECTIVECYLINDER-ENGAGING RINGS CONVERGE TOWARD SAID AXIS; (3) AN OPPOSITE SIDEFACE HAVING A CIRCUMFERENTIALLY EXTENDING AXIALLY PROJECTING RIBINTERMEDIATE SAID PERIPHERAL FACES, SAID RIB PROVIDING ANEXPANDERTHRUST-RECEIVING-SURFACE WHICH MAKES AN ANGLE OF NOT MORE THAN90* WITH SAID OPPOSITE SIDE FACE AND WHICH SURFACE IS LOCATED CLOSER TOSAID INNER PERIPHERAL FACE THAN TO SAID OUTER PERIPHERAL FACE; SAIDGROOVE HAVING A SUB-GROOVE EMBRACING THE INNER PERIPHERY OF THEUPPERMOST ONE OF SAID CYLINDER-ENGAGING RINGS AND ENGAGING THE OPPOSITESIDE (3) THEREOF ADJACENT ITS INNER PERIPHERY; SAID RINGS BEING DISPOSEDWITH THEIR RESPECTIVE RIBS ADDRESSED TOWARD EACH OTHER AND THEEXPANDER-THRUST-RECEIVING-SURFACE OF EACH RIB BEING SO ENGAGED WITH SAIDEXPANDER SPRING THAT THE RADIALLY OUTWARD BIASING ACTION OF THE EXPANDERIS DELIVERED TO SAID RIBS SUBSTANTIALLY FREE OF COMPONENTS WHICH TEND TODECREASE THE CONVERGING RELATIONSHIP BETWEEN THE FIRSTMENTIONED SIDEFACES OF THE RESPECTIVE CYLINDER-ENGAGING RINGS.